Universal reticle transfer system

ABSTRACT

A specially adapted SMIF pod ( 20 ) receives and holds one particular type of reticle cassette ( 36 ) or reticle holder ( 132 ) selected from among dozens of different configurations thereof. The SMIF pod ( 20 ) may be interrogated to determine the particular type of reticle cassette ( 36 ) or reticle holder ( 132 ) carried therein. A reticle transfer system ( 50 ) receives a pair of such SMIF pods ( 20 ), interrogates each of the SMIF pods ( 20 ) to ascertain which type of reticle cassette ( 36 ) or reticle holder ( 132 ) the SMIF pod ( 20 ) carries, and automatically moves reticles ( 42 ) through a controlled environment from one reticle cassette ( 36 ) or reticle holder ( 32 ) to another reticle cassette ( 36 ) or reticle holder ( 132 ). A reticle reorienter ( 56 ) includable in the system ( 50 ) also permits automatically exchanging reticles ( 42 ) between a reticle carrier ( 144 ) and a reticle cassette ( 36 ) or reticle holder ( 132 ).

TECHNICAL FIELD

The present invention relates generally to the technical field ofautomated tools used for integrated circuit fabrication and, moreparticularly, to automated reticle handling tools.

BACKGROUND ART

Presently, conventional processes for manufacturing integrated circuits(“ICs”) include a number of process steps in which a surface of asemiconductor wafer is first coated with a thin layer of a photo-resistmaterial after which the photo-resist material is irradiated with shortwavelength light to form a latent image of a pattern in the photo-resistlayer. A subsequent processing step develops the latent image therebyleaving patterned photo-resist material on a wafer's surface. Inprocessing a semiconductor wafer to fabricate ICs, the precedingprocedure for establishing patterned photo-resist material on a wafer'ssurface may be repeated dozens of times.

In irradiating photo-resist material, the short wavelength light used informing the latent image passes first through a reticle before impingingupon the thin layer of photo-resist material. In general, reticles usedin IC fabrication are made from a thick, planar, rectangularly or squareshaped pieces of glass. The reticle is opaque in those areas of thepattern where the reticle blocks the short wavelength light fromimpinging upon the thin layer of photo-resist material. The patternformed in the photo-resist layer on a wafer's surface generally differsfor each of the dozens of photo-resist exposures performed during ICfabrication. Thus, fabricating a particular type of IC may require adozen or more reticles.

Because reticles are high precision optical devices, they arecomparatively expensive. Each individual reticle can cost between$5,000.00 and $30,000.00 depending upon the size of the smallest featurein the pattern to be formed in the photo-resist layer on the wafer'ssurface. Consequently, a complete set of reticles needed for fabricatinga single type of IC may cost several hundred thousand dollars.Correspondingly, the photolithographic equipment which receives both thereticle and the wafer for exposing the photo-resist layer to shortwavelength light is also comparatively expensive costing several milliondollars.

A typical IC factory, commonly referred to as a “fab,” may includeseveral different models of photolithographic equipment from differentmanufacturers, or different models of photolithographic equipment fromthe same manufacturer. While these differing models of photolithographicequipment will all accept the same set of reticles used in manufacturinga single type of IC, previously there has existed no standard cassettefor holding the set of reticles while individual reticles areautomatically loaded into and removed from the photolithographicequipment. That is, individual photolithographic equipment manufacturershave arbitrarily selected unique configurations for cassettes used forholding reticles while individual reticles are automatically loaded intoand removed from the photolithographic equipment. Thus, worldwidepresently there are in daily use in IC fabs reticle cassettes havingdozens of different, incompatible configurations. Consequently, if a setof reticles for manufacturing a particularly type of IC are loaded intoa cassette for a particular type of photolithographic equipment and thatparticular photolithographic equipment is unavailable while anothermodel of photolithographic equipment is available, presently thereticles must be manually moved from one style of cassette that isincompatible with the available photolithographic equipment to anotherstyle of cassette that is compatible with the availablephotolithographic equipment.

In an effort to standardize reticle cassettes among the products ofvarious photolithographic equipment manufacturers, recentlySemiconductor Equipment and Materials International (“SEMI”) has adopteda standard, i.e. SEMI E100-0302, entitled “Specification for a ReticleSMIF Pod (RSP) Used to Transport and Store 6 Inch or 230 mm Reticles.”As implied by the name of the SEMI standard, the configuration of RSP isan adaptation of a previously existing Standard Mechanical InterFace(“SMIF”) pod which is widely used in IC fabs for carrying 8-inchsemiconductor wafers during wafer processing. While it appears likelythat sometime in the future all photolithographic equipment will acceptthe RSP for holding a set of reticles while individual reticles areautomatically loaded into and removed from the photolithographicequipment, due to the presently existing large installed base ofphotolithographic equipment such a situation is unlikely to occur in theimmediately foreseeable future. Thus, for the foreseeable future a needwill continue to exist for automatically moving reticles from one styleof cassette to another style of cassette.

Other considerations existing in conventional photolithographicprocessing exacerbate the need to move reticles from one style ofcassette to another style of cassette. The physical properties of thethin photo-resist layer degrade over time. While the severity of suchdegradation increases with the interval that elapses between coating awafer's surface and exposing the photo-resist material, depending uponprecise characteristics of environmental conditions to which thephoto-resist layer is exposed, the interval after which the yield ofgood ICs from a wafer becomes economically unacceptable can be as shortas tens of minutes up to several hours. Thus, once a wafer has beencoated with a thin layer of photo-resist material there exists asignificant economic incentive to expose the photo-resist layer asquickly as practicable. Consequently, if reticles for a particular typeof IC are held in a cassette for a model of unavailablephotolithographic equipment, there exists a correspondingly significanteconomic incentive to quickly move the reticles from one style ofcassette to another style of cassette that is compatible with anavailable model of photolithographic equipment. However, a lack ofcommonality among the dozens of different reticle cassetteconfigurations has prevented the development of automatic equipment fortransferring reticles between cassettes having differing configurations.

As is well known to those skilled in the art of IC fabrication,contamination must be reduced as much as practicable, or even eliminatedif possible, within an IC fab. Consequently any automatic equipment fortransferring reticles between cassettes having differing configurationsmust preserve the cleanliness of the fab, particularly cleanliness ofreticles passing through the equipment.

DISCLOSURE OF INVENTION

An object of the present invention is to provide SMIF pods that areadapted for receiving and holding a reticle cassette or reticle holderhaving a particular configuration.

Another object of the present invention is to provide SMIF pods thatcarry a unique, machine-readable code for specifying which particulartype of reticle cassette or reticle holder that the SMIF pod is adaptedto receive and hold.

Another object of the present invention is to provide a reticle transfersystem that effects automatic transfer of reticles between a pair ofreticle cassettes and/or reticle holders.

Another object of the present invention is to provide a reticle transfersystem which moves reticles automatically between a pair of reticlecassettes and/or reticle holders through a controlled environmentmaintained within the reticle transfer system.

Another object of the present invention is to provide a reticle transfersystem which ascertains from a unique, machine-readable code carried bya SMIF pod which particular type of reticle cassette or reticle holderthe SMIF pod carries.

One aspect of the present invention provides an adaptation of the SMIFpod that permits receiving and holding one particular type of reticlecassette or reticle holder from among the dozens of differentconfigurations. The present invention further provides a SMIF pod whichmay be interrogated to establish the particular type of reticle cassetteor reticle holder carried within the SMIF pod.

Another aspect of the present invention is a reticle transfer systemthat:

-   -   1. receives a pair of SMIF pods that have been adapted to        receive and hold one particular type of reticle cassette or        reticle holder from among dozens of different configurations;    -   2. interrogates each of the SMIF pods to ascertain the        particular type of reticle cassette or reticle holder        configuration carried by the SMIF pod; and    -   3. automatically moves reticles through a controlled environment        from a reticle cassette or reticle holder in one of the SMIF        pods to a reticle cassette or reticle holder in the other SMIF        pod where the cassettes or reticle holders have differing        configurations.

These and other features, objects and advantages will be understood orapparent to those of ordinary skill in the art from the followingdetailed description of the preferred embodiment as illustrated in thevarious drawing figures.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view that depicts a SMIF pod;

FIG. 2 is a perspective view that depicts a base of a SMIF pod that hasbeen adapted to receive and hold a particular type of reticle-holdingcassette or reticle holder;

FIG. 3 is a perspective view that depicts a that includes a plurality ofSMIF pod openers which is adapted for automatically moving reticlesbetween pairs of reticle-holding cassettes or reticle holders carriedwithin SMIF pods, and that also includes a reticle reorienter;

FIG. 4 is a perspective view that depicts a pair of SMIF pods such asmay be received into adjacent SMIF pod openers included in the systemdepicted in FIG. 3;

FIG. 5 is a perspective view that depicts a pair of bases of SMIF podsthat respectively carry reticle-holding cassettes which SMIF pod openershave exposed by removing the SMIF covers therefrom;

FIG. 6 is an exploded perspective view that depicts a first embodimentof end effector adapted for attachment to an otherwise conventionalrobotic arm mechanism included in the system depicted in FIG. 3 whichadapts the robotic arm mechanism for gripping reticles that are carriedin reticle-holding cassettes such as those depicted in FIG. 5, or inreticle holders;

FIG. 7 is a perspective view that depicts a reticle cassette having astructure which prevents an end of the end effector depicted in FIG. 6from extending past an edge of a reticle carried therein that is distalfrom the system's robotic arm mechanism;

FIG. 8 is an exploded perspective view that depicts a second embodimentfor end effector adapted for attachment to an otherwise conventionalrobotic arm mechanism included in the system depicted in FIG. 3 whichadapts the robotic arm mechanism for gripping reticles that are carriedin reticle cassettes;

FIGS. 9A and 9B respectively depict reticle holders each of whichreceives and holds only a single reticle;

FIG. 10 is a perspective view that depicts one particular type ofreticle-shipping container having an outer box which receives a reticlecarrier that holds vertically oriented reticles;

FIG. 11A is a perspective view depicting one side of the reticle carriertaken along a line 11A-11A in FIG. 10;

FIG. 11B is a perspective view depicting another side of the reticlecarrier taken along a line 11B-11B in FIG. 11A;

FIG. 12A is a perspective view depicting one embodiment of the reticlereorienter called a tilt station as it appears to an operator beforeplacing the reticle carrier depicted in FIGS. 11A and 11B thereon;

FIG. 12B is a perspective view depicting the tilt station taken along aline 12B-12B in FIG. 12A as the tilt station appears when viewed fromwithin the reticle transfer system, and when the tilt station ispositioned so a reticle carrier as may be held thereby is properlyoriented for exchanging reticles with a reticle cassette or with areticle holder;

FIG. 13 is a perspective view depicting an alternative embodimentreticle reorienter called a box-opening station as it appears to anoperator before placing the reticle-shipping container depicted in FIG.10 thereon;

FIG. 14 is a perspective view depicting the box-opening station of FIG.13 with the reticle-shipping container of FIG. 10 placed thereon;

FIG. 15 is an enlarged perspective view taken along a line 15-15 in FIG.14 that depicts a portion of the outer box that carries the registrationtag, and a portion of the box-opening station which includes aorientation probe that interrogates the registration tag;

FIG. 16 is a perspective view depicting the box-opening station of FIG.13 with the reticle-shipping container placed thereon after successfullyscanning a registration tag to establish that the reticle-shippingcontainer is properly oriented within the reticle transfer system andtherefore ready for removing a box cover included therein;

FIG. 17 is a perspective view depicting the box-opening station of FIG.13 with the box cover of the reticle-shipping container removed, andwith the registration-tag scanner interrogating the registration tag;and

FIGS. 18A and 18B are perspective views of the box-opening station as itappears when viewed from within the reticle transfer system along a line18AB-18AB in FIG. 17, and when the box-opening station is positioned soa reticle carrier held thereby is oriented for exchanging reticles witha reticle cassette or with a reticle holder.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 illustrates a SMIF pod, referred to by the general referencecharacter 20, that includes a SMIF cover 24 and a SMIF base 26. Asdescribed in U.S. Pat. No. 5,984,610 that is incorporated herein byreference, when used for carrying semiconductor wafers, the SMIF cover24 of the SMIF pod 20 may be unlatched from the SMIF base 26 and raisedup to expose a wafer-carrier that was previously enclosed therein.

FIG. 2 illustrates an upper surface 28 of the SMIF base 26 of the SMIFpod 20 with the SMIF cover 24 removed. In the illustration of FIG. 2,L-shaped blocks 32 and pins 34 (only one of which is visible in FIG. 2)have been affixed to the SMIF base 26 thereby adapting the SMIF base 26to receive and hold one particular type of reticle cassette 36 selectedfrom among the dozens of different configurations for the reticlecassette 36. As illustrated in FIG. 2, received and held on the SMIFbase 26 the reticle cassette 36 supports several reticles 42 orientedparallel to the upper surface 28 of the SMIF base 26 in slots 44 thatmay be provided by various different structures depending upon theparticular type of reticle cassette 36.

FIG. 2 depicts one possible configuration of L-shaped blocks 32 and pins34 selected to adapt the SMIF base 26 to receive and hold one particulartype of reticle cassette 36. The specific configuration of structuresaffixed to the upper surface 28 of the SMIF base 26 will vary dependingupon the particular type of reticle cassette 36 which the SMIF base 26is adapted to receive and hold.

Also affixed to the SMIF base 26 is cassette-type encoder 48 whichcarries a unique, machine-readable code that specifies the particulartype of reticle cassette 36 that the SMIF base 26 is adapted to receiveand hold. The presently preferred embodiment of the cassette-typeencoder 48 is a block of material that is pierced by one or more holeswhich are oriented parallel to the upper surface 28 of the SMIF base 26.To ascertain the particular type of reticle cassette 36 that the SMIFbase 26 is adapted to receive and hold, the cassette-type encoder 48 maybe scanned parallel to the upper surface 28 of the SMIF base 26 by abeam of light to determine if a hole pierces the cassette-type encoder48 at preestablished locations arranged along the cassette-type encoder48.

FIG. 3 illustrates a universal reticle transfer system, referred to bythe general reference character 50, for automatically moving reticles42, through a controlled environment maintained within the reticletransfer system 50, between a pair of reticle cassettes 36 which mayhave differing configurations. The reticle transfer system 50 includesSMIF pod openers 52, at least two (2) but preferably three (3), whichpreferably are of the type described in U.S. Pat. No. 5,984,610. Two ofthe pod openers 52 respectively concurrently receive sealed SMIF pods 20carrying reticle cassettes 36 such as the SMIF pods 20 illustrated inFIG. 4. Each of the pod openers 52 then unlatches the SMIF cover 24 fromthe SMIF base 26 and raises the SMIF cover 24 upward from the SMIF base26 to thereby expose, as illustrated in FIG. 5, the reticle cassettes 36that are respectively carried on SMIF bases 26. The reticle transfersystem 50 also includes an operator's console 54 that is disposed to oneside of the pod openers 52. The reticle transfer system 50 furtherincludes an reticle reorienter 56 that is located on the opposite sideof the pod openers 52 from the operator's console 54.

Disposed within the reticle transfer system 50 is a mostly conventionalrobotic arm mechanism not illustrated in any of the FIGs. The roboticarm mechanism is capable of moving laterally within the reticle transfersystem 50 to confront any of the pod openers 52 or the reticlereorienter 56. The robotic arm mechanism is also adapted to movevertically up and down along, and to extend toward and retract from anyof the pod openers 52 or the reticle reorienter 56.

FIG. 6 depicts a first embodiment for an end effector 72 that isincluded in the robotic arm mechanism of the reticle transfer system 50.The end effector 72 is secured at an end of the robotic arm mechanism tobe, at various times, thereby positioned adjacent to one of the podopeners 52 or to the reticle reorienter 56. A top cover 74 and a bottomcover 76, when secured to a mounting plate 78, enclose variouscomponents of the end effector 72. Opposite sides of an end 82 of areticle-support blade 84, that projects outward from the mounting plate78 which is nearer to the robotic arm mechanism, respectively carry apair of front grippers 86. Opposite halves of a thru-beam fiber opticsensor 92 are also disposed at the end 82 of the reticle-support blade84, between the front grippers 86, and on opposite sides of an elongatednotch 94 that pierces the reticle-support blade 84. After the podopeners 52 open SMIF pods 20 by raising the SMIF covers 24 upward fromthe SMIF bases 26 thereby exposing the reticle cassettes 36, the roboticarm mechanism may move the notch 94 in the mounting plate 78 along theSMIF base 26 about the cassette-type encoder 48 so a beam of lightpassing between opposite halves of the thru-beam fiber optic sensor 92interrogates the cassette-type encoder 48 for the presence or absence ofholes piercing the cassette-type encoder 48 at preestablished locations.In this way the reticle transfer system 50 may ascertain the particulartype of reticle cassette 36 that each SMIF base 26 is adapted to receiveand hold.

While the cassette-type encoder 48 and the thru-beam fiber optic sensor92 are the presently preferred embodiment of the invention forascertaining the particular type of reticle cassette 36 that each SMIFbase 26 is adapted to receive and hold, it is readily apparent thatthere exist various alternative ways in which this could beaccomplished. Thus, to permit ascertaining the particular type ofreticle cassette 36 that each SMIF base 26 is adapted to receive andhold, a SMIF base 26 in accordance with the present invention may beequipped, for example, with an ID tag that is read using a radiofrequency transmission, a reflective/scattering optical ID tag such as abar code tag, a magnetic stripe ID tag, an ID tag that is read bymechanical contact, an ID tag that is read pneumatically, an ID tag thatis read acoustically, etc.

In addition to the thru-beam fiber optic sensor 92, also mounted at theend 82 of the mounting plate 78 to one side of the thru-beam fiber opticsensor 92 is an optical reticle-presence sensor 98. After the reticletransfer system 50 using the thru-beam fiber optic sensor 92 on the endeffector 72 has ascertained the particular type of reticle cassette 36that is present on the SMIF base 26, the reticle transfer system 50moves the end effector 72 vertically along an edge of the reticlecassette 36 resting on the SMIF base 26. In accordance with thedisclosure of U.S. Pat. No. 6,013,920 that is hereby incorporated byreference, using electrical signals produced by the reticle-presencesensor 98 the reticle transfer system 50 is able to ascertain where thereticle cassette 36, i.e. which of the slots 44 in the reticle cassette36, actually carries a reticle 42.

Having thus determined which slots 44 within the two reticle cassettes36 carry reticles 42 and which slots 44 are empty, the reticle transfersystem 50 then proceeds to move reticles 42, one-by-one, from one of thereticle cassettes 36 to empty slots 44 in the other reticle cassette 36.In moving each reticle 42, the robotic arm mechanism inserts the endeffector 72 horizontally beneath the reticle 42 until the grooved frontgrippers 86 are positioned to receive an edge of the reticle 42 that islocated furthest from the mounting plate 78 and from the robotic armmechanism. After the grooved front grippers 86 are positioned to receivean edge of the reticle 42, the reticle transfer system 50 raises the endeffector 72 until the grooved front grippers 86 engage that edge of thereticle 42. After the grooved front grippers 86 engage the edge of thereticle 42, a pneumatic cylinder 102 included in the end effector 72urges a rear gripper 104 horizontally toward the edge of the reticle 42that is nearest to the mounting plate 78, i.e. furthest from the frontgrippers 86. Angled surfaces 108, located at opposite ends of the reargripper 104, engage opposite corners of the reticle 42 and urge ittoward a centered position on the end effector 72.

With the end effector 72 thus supporting and clamping the reticle 42between the front grippers 86 and the rear gripper 104, the robotic armmechanism then withdraws the reticle 42 from the reticle cassette 36into the controlled environment within the reticle transfer system 50,and then moves laterally to the other reticle cassette 36 and verticallyto an empty slot 44 in the reticle cassette 36. Thus positioned adjacentto an empty slot 44, the robotic arm mechanism inserts the end effector72 and the reticle 42 clamped thereto into the empty slot 44 to depositthe reticle 42 therein. Having thus moved one reticle 42 from onereticle cassette 36 to another reticle cassette 36, the reticle transfersystem 50 repeats the process until all specified reticles 42 have beenmoved from one reticle cassette 36 to the other reticle cassette 36.

One operational condition for which the reticle transfer system 50 asdescribed thus far is unsuitable is removing reticles 42 from andinserting reticles 42 into reticle cassettes 36 where the structure ofthe reticle cassette 36 prevents the end 82 of the end effector 72 fromextending past the edge of the reticle 42 furthest from the mountingplate 78. FIG. 7 illustrates one such type of reticle cassette 36 whichincludes a pair of cruciform bars 112 which span one opening 114 in thereticle cassette 36 to thereby prevent reticles 42 from passingtherethrough. To permit initially engaging reticles 42 that are held insuch reticle cassettes 36, the rear gripper 104 of the end effector 72illustrated in FIG. 6 includes a vacuum port 116. After extending therear gripper 104 furthest from the mounting plate 78, using thepneumatic cylinder 102 the reticle transfer system 50 causes the endeffector 72 to engage the reticle 42 thereby establishing with thevacuum port 116 a vacuum chuck which secures the reticle 42 to the endeffector 72.

With the reticle 42 now secured to the end effector 72, the reticletransfer system 50 causes the end effector 72 to retract a shortdistance along the slots 44 thereby establishing a space within thereticle cassette 36 depicted in FIG. 7 beyond the reticle 42 into whichthe end 82 may now be positioned beyond the edge of the reticle 42furthest from the mounting plate 78. After moving the reticle 42 thisshort distance, the end effector 72 releases the reticle 42. With thereticle 42 thus positioned so the front grippers 86 of the end effector72 may now engage the edge of the reticle 42 furthest from the mountingplate 78, the reticle transfer system 50 then proceeds to grasp and movethe reticle 42 as described previously.

After the reticle 42 has been moved to a slot 44 in the other reticlecassette 36, if the structure of the receiving reticle cassette 36 barsthe end effector 72 from inserting the reticle 42 fully into the slot44, the reticle transfer system 50 deposits the reticle 42 part wayalong the slot 44, releases the reticle 42, and then using the reargripper 104 nudges the reticle 42 the remaining distance along the slot44 until the reticle 42 is fully inserted into the reticle cassette 36.

FIG. 8 illustrates a second embodiment for the end effector 72. Thoseelements depicted in FIG. 8 that are common to the end effector 72illustrated in FIG. 6 carry the same reference numeral distinguished bya prime (“′”) designation. The end effector 72′ depicted in FIG. 8differs from the end effector 72 depicted in FIG. 6 by having a fixed,rather than moving, rear gripper 104′, and by including a pair ofmoveable side grippers 122. Secured at an end of each side gripper 122is U-shaped reticle clamp 124. The reticle clamps 124 are respectivelyshaped to receive and mate with an edge of the reticle 42 when theyclose toward each other along arcuate paths illustrated by curved arrows126 in FIG. 8. While the reticle clamps 124 engage opposite sides of areticle 42 thereby clamping the reticle 42 to the end effector 72′, theside grippers 122 particularly restrain the reticle 42 from movinghorizontally with respect to the reticle-support blade 84′. Though notillustrated in any of the FIGS., as is readily apparent the reticleclamps 124 may close toward each other along a linear path rather thanthe arcuate paths indicated by the curved arrows 126 in FIG. 8.

In addition to the arcuate motion of the reticle clamps 124 for grippingand releasing the reticle 42, as indicated by straight arrows in FIG. 8both of the side grippers 122 are moveable laterally both toward andaway from the end 82′ of the end effector 72′. Such linear motion of thereticle clamps 124 permits them to be positioned to avoid colliding withvarious different types of reticle cassettes 36 when engaging a reticle42 carried therein.

There exists yet a third embodiment for the end effector 72 whichcombines the reticle gripping aspects of both embodiments describedabove and depicted respectively in FIGS. 6 and 8. Accordingly, thisthird embodiment for the end effector 72 includes both the moveable reargripper 104 and the moveable side grippers 122. Thus, while theembodiments for the end effector 72 depicted in FIGS. 6 and 8respectively grip the reticle 42 either along edges thereof which aretransverse to the reticle-support blade 84 in the instance of FIG. 6, orparallel to the reticle-support blade 84′ in the instance of FIG. 8, thethird embodiment for the end effector 72 grips the reticle 42 alongedges thereof which are both transverse to and parallel to thereticle-support blade 84.

In addition to reticle cassettes 36 which are capable of simultaneouslyreceiving and holding a number of reticles 42, there exist reticleholders 132, such as those respectively depicted in FIGS. 9A and 9Bwhich, which have differing configurations, and which receive and holdonly a single reticle 42. While reticle cassettes 36 whichsimultaneously receive and hold a number of reticles 42 are used almostexclusively during reticle fabrication, reticle holders 132, such asthose respectively depicted in FIGS. 9A and 9B which receive and holdonly one (1) reticle 42, are used both during reticle fabrication, andduring IC fabrication. To protect reticles 42 from contamination, inaccordance with the present invention SMIF bases 26 of SMIF pods 20 arealso specifically adapted, in a manner similar to that describedpreviously for the reticle cassettes 36, to receive and hold aparticular type of reticle holder 132, such as those illustrated inFIGS. 9A and 9B, that receives and holds only one (1) reticle 42.

In removing a reticle 42 from either type of reticle cassette 36depicted respectively in FIGS. 9A and 9B, generally the reticle-supportblade 84 of the end effector 72 or 72′ first moves beneath the reticle42 until the front grippers 86 extend beyond the far edge of the reticle42. When the front grippers 86 extend beyond the far edge of the reticle42, the robotic arm mechanism raises the end effector 72 or 72′ first toengage the reticle 42 and then to elevate it above projecting posts 136which are shaped to receive and hold the reticle 42. After the reticle42 has been raised above the posts 136, either of the gripper mechanismsdescribed above which are respectively depicted in FIGS. 6 and 8, or acombination thereof, are activated to clamp the reticle 42 to the endeffector 72 before beginning to move the reticle 42 to a reticlecassette 36 or to a different type of reticle holder 132. The reticletransfer system 50 may deliver each reticle 42 removed from a reticleholder 132 to a slot 44 in a reticle cassette 36 as described above.Alternatively, the reticle transfer system 50 may place individualreticle 42 onto the posts 136 of any of the various styles of reticleholders 132 by reversing the process described above for removing thereticle 42 from the reticle holder 132.

Reticles initially arrive at an IC fab in various different styles ofhighly specialized shipping containers. FIG. 10 illustrates oneparticular type of shipping container, called a Hoya container, that isidentified in that FIG. by the general reference character 140. The Hoyareticle-shipping container 140 includes a hollow outer box 142 whichreceives a separate inner reticle carrier 144. Mating structures on anouter surface of the reticle carrier 144 and on an inner surface of theouter box 142 constrain the outer box 142 to receive the reticle carrier144 in only one orientation.

A box cover 146, included in the reticle-shipping container 140, matessnugly with the outer box 142 to seal a reticle carrier 144 carryingvertically oriented reticles 42 within a closed reticle-shippingcontainer 140. A pair of cover catches 152 that are located on oppositesides of the box cover 146, only one of which appears in FIG. 10,project downward toward the outer box 142. Rectangularly shapedapertures 154, which pierce each of the cover catches 152, respectivelymate with tabs 156 which protrude outward from opposite outer surfacesof the outer box 142. Engagement of the apertures 154 with theirrespective tabs 156 locks the box cover 146 onto the outer box 142. Asingle triangularly shaped registration tag 158, that protrudes from anouter surface of the outer box 142, indicates the orientation of thereticle carrier 144 within a sealed reticle-shipping container 140. Thebox cover 146 also includes a similar, triangularly shaped registrationtag 159.

The reticle transfer system 50 includes the reticle reorienter 56 topermit automatically exchanging reticles 42 between a reticle carrier144 and a reticle cassette 36 or a reticle holder 132. When reticles 42are transported outside of a SMIF pod 20 in the reticle-shippingcontainer 140, the reticles 42 are usually oriented vertically to reduceany possibility that the reticles 42 might be dropped or becomecontaminated. To provide compatibility with this mode of reticletransportation, as described in greater detail below, the reticlereorienter 56 in one embodiment accepts just the reticle carrier 144 inwhich the reticles 42 are oriented vertically, rotates the reticlecarrier 144 90° about a horizontal axis until the reticles 42 areoriented horizontally. Another embodiment of the reticle reorienter 56,also described in greater detail below, accepts the entirereticle-shipping container 140 carrying the reticle carrier 144 togetherwith the vertically oriented reticles 42, removes the box cover 146, andthen rotates the outer box 142 together with the reticle carrier 144 90°about a horizontal axis until the reticles 42 are oriented horizontally.After either embodiment of the reticle reorienter 56 orients thereticles 42 horizontally, the end effector 72 may grasp individualreticles 42 and move them to a reticle cassette 36 or to a reticleholder 132 that is located in one of the pod openers 52. Similarly,either embodiment of the reticle reorienter 56 may re-orient reticles 42from a horizontal orientation in which they are received from a reticlecassette 36 or from a reticle holder 132 to a vertical orientation inthe reticle carrier 144 for transfer out of the reticle transfer system50.

In addition to permitting automatic exchange of reticles 42 between areticle carrier 144 and a reticle cassette 36 or a reticle holder 132,the reticle reorienter 56 may also be used advantageously for bufferingexcess reticles 42. Thus, for example, if a reticle cassette 36 fromwhich the reticle transfer system 50 is removing reticles 42 holds morereticles 42 than the reticle cassette 36 or reticle holder 132 to whichthe reticle transfer system 50 is transferring the reticles 42, thenexcess reticles 42 may be stored temporarily into a reticle carrier 144that is present in the reticle reorienter 56. Subsequently, the reticletransfer system 50 may move the reticles 42 stored temporarily in thereticle carrier 144 into empty slots 44 in a reticle cassette 36 or in areticle holder 132 that is subsequently loaded into one of the podopeners 52. Alternatively, the reticle transfer system 50 may alsoinclude a mini-stocker to provide the reticle transfer system 50 with acapability for buffering excess reticles 42.

FIGS. 11A and 11B respectively illustrate from differing viewpoints thereticle carrier 144 that is included in the Hoya reticle-shippingcontainer 140. FIG. 11A illustrates differing size cavities 172A and172B formed in an outer surface 174 of the reticle carrier 144. Asstated previously, differing sizes of the cavities 172A and 172B incombination with corresponding structures on the inner surface of theouter box 142 constrain the outer box 142 to receive the reticle carrier144 in only one orientation. FIG. 11A also clearly depicts slots 176included in the reticle carrier 144 each pair of which disposed alongopposite sides of the reticle carrier 144 receives a single reticle 42.The illustration of FIG. 11B shows two sets of five (5) trapezoidallyshaped apertures 182 which pierce a bottom surface 184 of the reticlecarrier 144 at the base of each of the slots 176.

FIG. 12A illustrates one embodiment of the reticle reorienter 56 calleda tilt station that is identified by the general reference character200. The illustration of FIG. 12A depicts the tilt station 200 as itappears to an operator of the reticle transfer system 50 before placinga reticle carrier 144 thereon.

The tilt station 200 includes an open, box-shaped carrier receiver 202which is supported between two bulkheads 204A and 204B for rotationabout a horizontal axis 206. In the illustration of FIG. 12A, two rowscontaining five pin 212s each project upward from a horizontallyoriented carrier table 214 included in the carrier receiver 202. A firstpair of retaining plates 216A and 216B also project from the carriertable 214 respectively across opposite ends of the rows of pins 212. Asecond pair of retaining plates 218A and 218B similarly project from thecarrier table 214 respectively parallel to and outward from the rows ofpins 212. The size and arrangement of the pins 212 on the carrier table214 adapt each of them to enter into and mate snugly with one of theapertures 182 which pierce the bottom surface 184 of the reticle carrier144 depicted in FIG. 11B. The shape and location of the retaining plates216A, 216B, 218A and 218B on the carrier table 214 juxtaposes them withthe outer surface 174 of a reticle carrier 144 installed on the pins212. Edges of the retaining plates 216A, 216B, 218A and 218B furthestfrom the carrier table 214 and nearest to the pins 212 are chamfered forguiding a reticle carrier 144 onto the pins 212.

When an operator of the reticle transfer system 50 removes the reticlecarrier 144 from the reticle-shipping container 140 and places it ontothe carrier table 214 in the orientation illustrated in FIG. 12A,reticles 42 present in the reticle carrier 144 are oriented vertically.To permit automatically exchanging reticles 42 between the reticlecarrier 144 present in the tilt station 200 embodiment of the reticlereorienter 56 and a reticle cassette 36 or a reticle holder 132 presentand exposed in one of the pod openers 52, an electrical motor 222secured to the bulkhead 204B rotates the carrier receiver 202 90° aboutthe axis 206 until the carrier table 214 becomes oriented vertically asillustrated in FIG. 12B. Frictional engagement between the reticlecarrier 144 and the pins 212 and retaining plates 216A, 216B, 218A and218B of the tilt station 200 retains the re-oriented reticle carrier144, in which reticles 42 are now oriented horizontally, in the carrierreceiver 202. With reticles 42 in the reticle carrier 144 thus orientedhorizontally, using the end effector 72 or 72′ the robotic arm mechanismmay, in the manner described previously, effect an exchange of reticles42 between the reticle carrier 144 and a reticle cassette 36 or areticle holder 132 present and exposed in one of the pod openers 52.

FIG. 13 is a perspective view depicting an alternative embodimentreticle reorienter 56 called a box-opening station that is referred toby the general reference character 250. The box-opening station 250includes a tilt table 252 which is supported for rotation about ahorizontal axis 254 by a pair of bulkheads 256A and 256B. The tilt table252 carries a rotary table 262 which turns about a vertical axis 264. Aset of box guides 266 are secured to the rotary table 262 arranged in arectangular shape which snugly receives the outer box 142 of thereticle-shipping container 140. Edges of the box guides 266 about theperimeter of the rectangular shape are chamfered for guiding the outerbox 142 onto the rotary table 262 as illustrated in FIG. 14.

After an operator places the outer box 142 of the reticle-shippingcontainer 140 onto the rotary table 262, the reticle transfer system 50checks the orientation of the outer box 142 to ascertain an orientationfor the reticle carrier 144 carried therein. The reticle transfer system50 checks the orientation of the outer box 142 by rotating anorientation-probe arm 272 of an orientation probe that is supported fromthe bulkhead 256B horizontally about a vertical axis 274 as indicated bya curved arrow 276. In this way the reticle transfer system 50juxtaposes a probe head 278 carried at a distal end of theorientation-probe arm 272 with the outer surface of the outer box 142.

With the reticle-shipping container 140 oriented as illustrated in 14,the probe head 278 fails to sense the registration tag 158 thatprotrudes from an outer surface of the outer box 142. When the reticletransfer system 50 fails to find the registration tag 158, theorientation-probe arm 272 rotates away from the outer box 142 and therotary table 262 carrying the reticle-shipping container 140 rotates180° about the axis 264 which is oriented parallel to reticles 42carried by the reticle carrier 144 of the reticle-shipping container140. Having now positioned the outer box 142 in this alternativeorientation, for a second time the orientation-probe arm 272 rotatesabout the axis 274 to juxtapose the probe head 278 with the outersurface of the outer box 142 as illustrated in FIG. 15. In this way thereticle transfer system 50 initially ensures that the orientation of thereticle-shipping container 140 places the registration tag 158protruding from the outer box 142 near the bulkhead 256B.

With the reticle-shipping container 140 now properly oriented on thetilt table 252 in the illustration of FIG. 16, as indicated by an arrow282 a lid-lifting arm 284 supported from the bulkhead 256A descendsuntil four suction cups 286 contact the box cover 146 of thereticle-shipping container 140. The reticle transfer system 50 thenapplies vacuum to the suction cups 286 thereby clamping the box cover146 thereto.

For the embodiment of the box-opening station 250 depicted in FIGS.13-16, an operator in placing the reticle-shipping container 140 ontothe rotary table 262 releases the engagement between the cover catches152 and the tabs 156. Alternatively, for automatically releasing theengagement between the cover catches 152 and the tabs 156 while anoperator places the reticle-shipping container 140 onto the rotary table262, the rotary table 262 may include two upwardly projecting bladesjuxtaposed with box guides 266 located on opposite sides of therectangular area enclosed by the box guides 266. Projecting ends of theblades will then slip between the cover catches 152 and the outer box142 while an operator places the reticle-shipping container 140 onto therotary table 262 thereby releasing the box cover 146. With the box cover146 released from the outer box 142 and with the suction cups 286clamping the box cover 146, the lid-lifting arm 284 rises as indicatedby an arrow 288 thereby opening the reticle-shipping container 140 asdepicted in FIG. 17 to thereby expose both the reticle carrier 144 andthe reticles 42 which it carries.

With the reticle carrier 144 thus exposed and resting within the outerbox 142, a pair of box clamps 292, that as most clearly illustrated inFIG. 13 are supported from the rotary table 262, rotate about ahorizontal axis 294 to engage one edge of the reticle carrier 144thereby locking the outer box 142 and the reticle carrier 144 to therotary table 262. With the outer box 142 and the reticle carrier 144locked to the rotary table 262, the tilt table 252 then rotates 90°about the axis 254 until the rotary table 262 becomes orientedvertically as illustrated in FIG. 18A. Orienting the rotary table 262vertically correspondingly orients reticles 42 in the reticle carrier144 horizontally. With reticles 42 in the reticle carrier 144 thusoriented horizontally, using the end effector 72 or 72′ the robotic armmechanism may, in the manner described previously, effect an exchange ofreticles 42 between the reticle carrier 144 and a reticle cassette 36 ora reticle holder 132 present and exposed in one of the pod openers 52.

As those skilled in the art are aware, reticles 42 usually carry apatterned layer of material, usually chromium, on only one surface tomake the reticle 42 opaque in those areas of the pattern where thereticle blocks short wavelength light from impinging upon the thin layerof photo-resist material. Consequently, depending upon how reticles 42are oriented within the reticle carrier 144, the orientation of reticles42 depicted in FIG. 18A may be opposite to that needed when the reticles42 are carried by a reticle cassette 36 or a reticle holder 132. Thebox-opening station 250 of the present invention addresses thispossibility by being adapted to effect a rotation of the rotary table262 180° about the axis 264 into the orientation depicted in FIG. 18B.However, the rotary table 262 does not move directly between theorientations respectively depicted in FIGS. 18A and 18B. In movingbetween those two orientations, the box-opening station 250 firstreturns the rotary table 262 to a horizontal orientation so reticles 42present in the reticle carrier 144 are oriented vertically. With thereticles 42 thus oriented vertically in the reticle carrier 144, it isimpossible for them to fall out of the reticle carrier 144 while therotary table 262 effects a 180° rotation. Having thus oriented thereticles 42 vertically, the reticle transfer system 50 first rotates therotary table 262 180° about the axis 264 and then rotates the tilt table252 90° about the axis 254 until the rotary table 262 becomes orientedvertically and the reticles 42 become oriented horizontally.

INDUSTRIAL APPLICABILITY

Some IC fabs employ a practice of orienting all reticles 42 but one in areticle carrier 144 in a particular direction. The remaining reticle 42is then oriented in an opposite direction. The orientations chosen forthe reticles 42 causes all layers of patterned material to face awayfrom the inner surface of the walls of the reticle carrier 144. Such amixed orientation for the reticles 42 reduces the possibility that thepatterned layer might become contaminated by anything present on or inthe walls of the reticle carrier 144. When exchanging reticles 42 whichemploy such an orientation in the reticle carrier 144 and a reticlecassette 36 or a reticle holder 132 present and exposed in one of thepod openers 52. the reticle transfer system 50 first places the rotarytable 262 in either of the orientations depicted respectively in FIG.18A or 18B. Having established one of these two orientations for thereticle carrier 144, the reticle transfer system 50 then effects anexchange of all properly oriented reticles 42 between the reticlecarrier 144 and a reticle cassette 36 or a reticle holder 132 presentand exposed in one of the pod openers 52. Those reticles 42 which areimproperly oriented remain in the reticle carrier 144. After all theproperly oriented reticles 42 have been exchanged, in the mannerdescribed above the reticle transfer system 50 effects a 180° of therotary table 262 about the axis 264 into an orientation in which theremaining reticles 42 are properly oriented for an exchange between thereticle carrier 144 and a reticle cassette 36 or a reticle holder 132present and exposed in one of the pod openers 52.

At any instant in time, large contract IC fabs, usually calledfoundries, may have an inventory of 3,000 to 6,000 different reticles42. This large number of unique reticles 42 permit the foundry tomanufacture a large number of different types of ICs, each differenttype of IC being manufactured in a quantity which responds to marketdemand therefor. However, maintaining order in such a large inventory ofdifferent reticles 42 is a herculean task. Thus a commerciallyavailable, conventional automated SMIF stocker not illustrated in any ofthe FIGs., such as the SMIF stocker disclosed in U.S. Pat. No.5,980,183, may be advantageously combined with the reticle transfersystem 50 for delivering SMIF pods 20 to the reticle transfer system 50containing a specified reticle 42 or set of reticles 42, and forreturning SMIF pods 20 containing reticles 42 from the reticle transfersystem 50 to the inventory of reticles 42 maintained in the SMIFstocker.

Although the present invention has been described in terms of thepresently preferred embodiment, it is to be understood that suchdisclosure is purely illustrative and is not to be interpreted aslimiting. Consequently, without departing from the spirit and scope ofthe invention, various alterations, modifications, and/or alternativeapplications of the invention will, no doubt, be suggested to thoseskilled in the art after having read the preceding disclosure.Accordingly, it is intended that the following claims be interpreted asencompassing all alterations, modifications, or alternative applicationsas fall within the true spirit and scope of the invention.

1. A reticle transfer system that is adapted for transferring reticlesused in integrated circuit (“IC”) fabrication between reticle cassettesand/or reticle holders having differing configurations, each reticlecassette or reticle holder being respectively carried within a sealedStandard Mechanical InterFace (“SMIF”) pod that is adapted for receivingand holding a reticle cassette or reticle holder having a particularconfiguration, each reticle cassette or reticle holder enclosedrespectively within a sealed SMIF pod carrying at least one reticle, thereticle transfer system comprising: a. at least two SMIF pod openersthat are respectively adapted for: i. receiving a sealed SMIF pod whichcarries either a reticle cassette or a reticle holder; ii. opening theSMIF pod thereby exposing either a reticle cassette or a reticle holdercarried therein together with a reticle carried thereby to a controlledenvironment maintained within the reticle transfer system; and b. arobotic arm mechanism which includes an end effector that is adapted forsupporting and clamping a reticle, the robotic arm mechanism at varioustimes being positionable within the reticle transfer system adjacent toan opened SMIF pod that is present within either of the pod openers and:i. for inserting the end effector toward the exposed reticle cassette orreticle holder for supporting and clamping a reticle carried thereby,and to withdraw the reticle from the reticle cassette or reticle holderinto the controlled environment maintained within the reticle transfersystem; and ii. for inserting the end effector having a reticlesupported by and clamped thereto from the controlled environmentmaintained within the reticle transfer system toward the exposed reticlecassette or reticle holder to deposit the reticle in the reticlecassette or reticle holder; whereby the reticle transfer system effectsautomatic transfer of reticles through the controlled environmentmaintained within the reticle transfer system between a pair of reticlecassettes and/or reticle holders.
 2. The SMIF pods, which pod openersincluded in the reticle transfer system of claim 1 are adapted toreceive, include a cassette-type encoder which carries a unique,machine-readable code for specifying a particular type of reticlecassette or reticle holder that the SMIF pod is adapted to receive andhold, the reticle transfer system of claim 1 further comprising a readerfor ascertaining from the cassette-type encoder which particular type ofreticle cassette or reticle holder a SMIF pod carries.
 3. Eachcassette-type encoder included in SMIF pods, which pod openers includedin the reticle transfer system of claim 2 are adapted to receive,include a block of material that is pierced by at least one hole andwhich is affixed to a base of the SMIF pod, and wherein the end effectorof the reticle transfer system of claim 2 includes a thru-beam sensorwhich, in ascertaining which particular type of reticle cassette orreticle holder the SMIF pod carries, is adapted for passing a beam oflight through holes that pierce the block of material.
 4. The reticletransfer system of claim 1 wherein the end effector includes areticle-presence detector that is adapted for use in ascertaining alocation where the reticle cassette or reticle holder actually carries areticle.
 5. The reticle transfer system of claim 1 wherein the endeffector includes: a reticle-support blade that is secured to, supportedby and projects outward from the robotic arm mechanism, and that therobotic arm mechanism, when effecting an automatic transfer of a reticlebetween a pair of reticle cassettes and/or reticle holders, disposesbeneath the reticle; and a front gripper secured to an end of thereticle-support blade which is furthest from the robotic arm mechanism,and that the robotic arm mechanism, when effecting an automatic transferof a reticle between a pair of reticle cassettes and/or reticle holders,disposes to receive an edge of the reticle that is located furthest fromthe robotic arm mechanism.
 6. The SMIF pods, which pod openers includedin the reticle transfer system of claim 5 are adapted to receive,include a cassette-type encoder formed by a block of material that ispierced by at least one hole to thereby establish a unique,machine-readable code for specifying a particular type of reticlecassette or reticle holder that the SMIF pod is adapted to receive andhold, the cassette-type encoder being affixed to a base of the SMIF pod,and wherein the reticle transfer system of claim 5 wherein the frontgripper of the end effector is divided into two halves which arerespectively secured to the end of the reticle-support blade on oppositesides of a notch that pierces the end of the reticle-support bladefurthest from the robotic arm mechanism; and the end effector furtherincludes a thru-beam sensor which, when the reticle transfer systemascertains which particular type of reticle cassette or reticle holderthe SMIF pod carries: passes a beam of light across the notch thatpierces the end of the reticle-support blade furthest from the roboticarm mechanism; and the robotic arm mechanism positions the end effectorso the beam of light may pass through holes that pierce the block ofmaterial.
 7. The reticle transfer system of claim 5 wherein the endeffector further includes a rear gripper that is located on thereticle-support blade between the front gripper and the robotic armmechanism, the rear gripper being urgeable horizontally along thereticle-support blade toward the front gripper to engage an edge of thereticle which is furthest from the front gripper when the end effectorclamps a reticle thereto.
 8. The reticle transfer system of claim 7wherein the rear gripper of the end effector includes a vacuum port thatis adapted for engaging the edge of the reticle which is furthest fromthe front gripper to form a vacuum chuck therewith which, duringwithdrawal of the reticle from the reticle cassette or reticle holderinto the controlled environment maintained within the reticle transfersystem, secures the reticle to the end effector.
 9. The reticle transfersystem of claim 5 wherein the end effector further includes a pair ofmoveable side grippers that are located on the reticle-support bladebetween the front gripper and the robotic arm mechanism, the sidegripper being adapted for closing toward each other to respectivelyengage opposite side edges of the reticle thereby both clamping thereticle to the end effector and restraining the reticle from movinghorizontally with respect to the reticle-support blade.
 10. The reticletransfer system of claim 1 further comprising a reticle reorienteradapted for use in automatically exchanging reticles between a reticlecarrier located in the reticle reorienter and a reticle cassette or areticle holder located in one of the pod openers.
 11. The reticletransfer system of claim 10 wherein the reticle reorienter furtherre-orients reticles between a vertical orientation of reticles presentin a reticle carrier and a horizontal orientation of reticles carriedeither by a reticle cassette or by a reticle holder located in one ofthe pod openers.
 12. The reticle transfer system of claim 11 wherein thereticle reorienter is a tilt station which is adapted for directlyreceiving the reticle carrier after removal from a reticle-shippingcontainer, when the tilt station initially receives the reticle carrierreticles present therein are oriented vertically.
 13. The reticletransfer system of claim 11 wherein the reticle reorienter is abox-opening station which is adapted for directly receiving areticle-shipping container which includes an outer box in which rests areticle carrier that receives reticles, the reticle carrier and reticlescarried thereby being covered by a box cover which mates with and sealsthe outer box; when the box-opening station initially receives thereticle-shipping container, reticles present in the reticle carriercontained in the reticle-shipping container are oriented vertically; thebox-opening station being further adapted for removing the box cover tothereby expose both the reticle carrier and reticles carried by thereticle carrier.
 14. The reticle transfer system of claim 13 wherein areticle-shipping container received by the box-opening station includesa registration tag for indicating the orientation of the reticle carrierenclosed therein, and the box-opening station includes an orientationprobe for ascertaining the orientation of a reticle-shipping containerreceived by the box-opening station.
 15. The reticle transfer system ofclaim 13 wherein the box-opening station further includes least one boxclamp for locking the outer box and the reticle carrier to thebox-opening station while the box cover is removed therefrom.
 16. Thereticle transfer system of claim 13 wherein the box-opening stationfurther includes a rotary table that receives a reticle-shippingcontainer and is adapted for rotating the reticle-shipping containerabout an axis that is disposed parallel to reticles carried in thereticle carrier enclosed within the reticle-shipping container.
 17. Asealable SMIF pod that is adapted for receiving and holding a reticlecassette or reticle holder having a particular configuration, thereticle cassette or reticle holder enclosed within the SMIF pod beingadapted for carrying at least one reticle used in IC fabrication, theSMIF pod being further adapted for automatic processing by a reticletransfer system that transfers reticles between reticle cassettes and/orreticle holders having differing configurations that are respectivelycarried within SMIF pods, the reticle transfer system including: a. atleast two SMIF pod openers that are respectively adapted for: i.receiving a SMIF pod which carries either a reticle cassette or areticle holder; ii. opening the SMIF pod thereby exposing either areticle cassette or a reticle holder carried therein together with areticle carried thereby; b. a reader that is adapted for ascertainingwhich particular type of reticle cassette or reticle holder a SMIF podcarries; and c. a robotic arm mechanism which includes an end effectorthat is adapted for supporting and clamping a reticle, the robotic armmechanism at various times being positionable within the reticletransfer system adjacent to an opened SMIF pod that is present withineither of the pod openers and: i. for inserting the end effector towardthe exposed reticle cassette or reticle holder for supporting andclamping a reticle carried thereby, and to withdraw the reticle from thereticle cassette or reticle holder; and ii. for inserting the endeffector having a reticle supported by and clamped thereto toward theexposed reticle cassette or reticle holder to deposit the reticle in thereticle cassette or reticle holder; the SMIF pod comprising: a base thatreceives and holds a reticle cassette or reticle holder having aparticular configuration; a cover which mates with and is securable tothe base for enclosing a reticle cassette or reticle holder received andheld thereon, and which is unlatchable and removable from the base toexpose a reticle cassette or reticle holder carried thereon; and acassette-type encoder which carries a unique, machine-readable code forspecifying a particular type of reticle cassette or reticle holder theSMIF pod receives and holds.
 18. The SMIF pod of claim 17 wherein thecassette-type encoder includes a block of material that is pierced by atleast one hole and which is affixed to the base of the SMIF pod.